Exchange constant and domain wall width in (Ga,Mn)(As,P) films with self-organization of magnetic domains

The incorporation of phosphorus into (Ga,Mn)As epilayers allows for the tuning of the magnetic easy axis from in-plane to perpendicular-to-plane without the need for a (Ga,In)As template. For perpendicular easy axis, using magneto-optical imaging a self-organized pattern of up- and down-magnetized domains is observed. Combining Kerr microscopy, magnetometry, and ferromagnetic resonance spectroscopy, the exchange constant and the domain wall width parameter are obtained as a function of temperature. The former quantifies the effective Mn-Mn ferromagnetic interaction. The latter is a key parameter for domain wall dynamics. The comparison with results obtained for (Ga, Mn)As/(Ga,In)As reveals the improved quality of the (Ga,Mn)As(1-y)P(y) layers regarding domain wall pinning, an increase in the domain wall width parameter and of the effective Mn-Mn spin coupling.